Method and apparatus for mapping and de-mapping in an optical transport network

ABSTRACT

The embodiments of the present invention disclose methods and apparatuses for mapping processing and de-mapping processing in an optical transport network. A Lower Order Optical Channel Data Unit (LO ODU) signal is mapped into a payload area of an Optical Channel Data Tributary (ODTU) signal in units of M bytes. M is equal to the number of tributary slots of a Higher Order Optical Channel Payload Unit (HO OPU) that are to be occupied by the ODTU signal, and M is an integer larger than 1. Overhead information is encapsulated to an overhead area of the ODTU signal. Thereafter, the ODTU signal is multiplexed into the HO OPU. In this way, an efficient and universal mode for mapping the LO ODU to the HO OPU is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/712,675, filed on Feb. 25, 2010, which claimsthe benefit of priority to Chinese Patent Application No.200910106028.2, filed on Mar. 9, 2009, both of the applications areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to the field of communicationtechnologies, and particularly, to a mapping technique in an opticaltransport network.

BACKGROUND

With the quick development of communication technologies, the OpticalTransport Network (OTN), with the advantages of flexible scheduling andmanagement of large capacity services, is increasingly becoming a majortechnology of the backbone transport network. In the OTN, client data isencapsulated into an Optical Channel Payload Unit (OPU), some overhead(OH) is added to the OPU to constitute an Optical Channel Data Unit(ODU), some OH and Forward Error Correction (FEC) is added into the ODUto constitute an Optical Channel Transport Unit (OTU), and is finallytransmitted in the form of OTU.

With the rapid development of data services, more and more clients adoptEthernet technology as the physical interface at the client side. It isforeseeable that in the coming years, the Ethernet services will keep acontinuous high-speed growth. However, the current OTN technology isdesigned based on speech services such as synchronous digital hierarchy(SDH), and cannot well support the development trend of data serviceslike Ethernet, thus studies are gradually carried out on the nextgeneration of OTN network (NG OTN). The NG OTN is supposed not only tomeet the requirements of services newly appeared, but also bear thecurrent OTN. Thus, how to map a Lower Order Optical Channel Data Unit(LO ODU) to a Higher Order Optical Channel Data Unit (HO ODU) is a focusbeing discussed in the industry. The LO ODU may be regarded as ODUk(k=0, 1, 2, 2e, 3, 3e) existing in the current OTN, and hereinrepresented as LO ODUk (k=0, 1, 2, 2e, 3, 3e). The HO ODU may beregarded as a data transmission unit of a higher rate, which belongs tothe category of the NG OTN and is used for bearing the LO ODU, and thecorresponding OPU is represented as HO OPUk (k=1, 2, 3, 3e, 4).

The conventional technical solution maps the standard ODUj (j=1, 2) (for20 ppm bit tolerance) into the OPUk (k=2, 3) in an asynchronous manner.The asynchronous method maps the ODUj signal into the OPUk through anadjustment policy of −1/0/+1/+2. With the asynchronous manner, a maximumbit error tolerance between ODU1 and OPU2 is −113 to +83 ppm, a maximumbit error tolerance between ODU1 and OPU3 is −96 to +101 ppm, and amaximum bit error tolerance between ODU2 and OPU3 is −95 to +101 ppm.

However, the conventional method is not suitable for mapping the LO ODUinto the HO ODU, e.g. for ODU2 e (100 ppm bit tolerance), etc. ODUflexof higher bit tolerance may occur, and the adjustment policy of−1/0/+1/+2 does not meet the requirement for mapping the LO ODU into theHO ODU.

SUMMARY

Embodiments of the present invention provide method and apparatus formapping and de-mapping in an Optical Transport Network (OTN), so as tomap a Lower Order Optical Channel Data Unit (LO ODU) signal into aHigher Order Optical Channel Payload Unit (HO ODU) universally andefficiently.

In the mapping method provided by the embodiments of the presentinvention, first, a Lower Order Optical Channel Data Unit (LO ODU)signal is mapped into a payload area of an Optical Channel DataTributary Unit (ODTU) signal in units, each unit including M bytes,where M is equal to the number of tributary slots of a Higher OrderOptical Channel Payload Unit (HO OPU) that are to be occupied by theODTU signal, and M is an integer larger than 1.

And, overhead information is encapsulated to an overhead area of theODTU signal.

Finally, the ODTU signal is multiplexed into the HO OPU.

The apparatus for processing data in an OTN, provided by the embodimentsof the present invention, includes a processor and a computer readablemedium having a plurality of computer executable instructions storedthereon. The instructions, when executed by the processor, cause theprocessor to perform the steps of the above mapping method.

In the de-mapping method provided by the embodiments of the presentinvention, first, a HO OPU is parsed to obtain an ODTU signal.

Then, de-map in units of M bytes to obtain a Lower Order Optical ChannelData Unit (LO ODU) signal from a payload area of the ODTU signal, whereM is equal to the number of tributary slots of the HO OPU that areoccupied by the ODTU, and M is an integer larger than 1.

The de-mapping apparatus, provided by the embodiments of the presentinvention, comprises a processor and a computer readable medium having aplurality of computer executable instructions stored thereon. Theinstructions, when executed by the processor, cause the processor toperform the steps of the above de-mapping method.

The embodiments of the present invention further provide a mappingapparatus in an OTN. The mapping apparatus includes a mapping unit, anencapsulating unit and a multiplexing unit. The mapping unit isconfigured to map a Lower Order Optical Channel Data Unit (LO ODU)signal into a payload area of an Optical Channel Data Tributary Unit(ODTU) signal in units, each unit including M bytes, where M is equal tothe number of tributary slots of a Higher Order Optical Channel PayloadUnit (HO OPU) that are to be occupied by the ODTU signal, and M is aninteger larger than 1. The encapsulating unit is configured toencapsulate overhead information to an overhead area of the ODTU signal.The multiplexing unit is configured to multiplexing the ODTU signal intothe HO OPU.

The embodiments of the present invention further provide a de-mappingapparatus in an OTN. The de-mapping apparatus includes a parsing unit, ade-mapping unit. The parsing unit is configured to parse a Higher OrderOptical Channel Payload Unit (HO OPU) to obtain an Optical Channel DataTributary Unit (ODTU) signal. The de-mapping unit is configured tode-map in units, each unit including M bytes, to obtain a Lower OrderOptical Channel Data Unit (LO ODU) signal from a payload area of theODTU signal, where M is equal to the number of tributary slots of the HOOPU that are occupied by the ODTU, and M is an integer larger than 1.

In the above embodiments, the encapsulated overhead information mayfurther include information indicating the number of the M-byte dataunits of the LO ODU signal that are mapped during a multi-frame period.

According to at least some of the embodiments of the present invention,a high-efficient and universal mode for mapping a LO ODU to a HO OPU isachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Technical solutions of the embodiments of the present invention will nowbe described, by way of non-limiting example, with reference to theaccompanying drawings. It is apparent that the following are just somedrawings for the embodiments of the present invention, and a personskilled in the art can obtain other drawings based on these drawingswithout creative efforts.

FIG. 1 is a flowchart of a mapping method in an OTN according to anembodiment of the present invention;

FIG. 2 is a schematic illustration of dividing an HO OPU into eight 1.25G tributary slots, according to an embodiment of the present invention;

FIG. 3 is a schematic illustration of a mapping mode according to anembodiment of the present invention;

FIG. 4 is a schematic illustration of another mapping mode according toan embodiment of the present invention;

FIG. 5 is a schematic illustration of a mapping from LO ODU to HO OPU2according to an embodiment of the present invention;

FIG. 6 is a schematic illustration of another mapping from LO ODU to HOOPU2 according to an embodiment of the present invention;

FIG. 7 is a schematic illustration of yet another mapping from LO ODU toHO OPU2 according to an embodiment of the present invention;

FIG. 8 is a schematic view illustrating information encoding of“C8M-base+C8M-delta+C8-delta” according to an embodiment of the presentinvention;

FIG. 9 is a flowchart of a de-mapping method in an OTN according to anembodiment of the present invention;

FIG. 10 is a simplified block diagram of a mapping apparatus in an OTNaccording to an embodiment of the present invention;

FIG. 11 is a simplified block diagram of a mapping apparatus in an OTNaccording to another embodiment of the present invention; and

FIG. 12 is a simplified block diagram of a de-mapping apparatus in anOTN according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions of the embodiments of the present invention aredescribed in the following in conjunction with the drawings of theembodiments. It is apparent that the described embodiments are just apart of embodiments of the present invention, instead of all embodimentsthereof. Based on the embodiments of the present invention as describedbelow, other embodiments, which may be obtained by a person skilled inthe art without creative efforts, shall also fall within the protectionscope of the present invention.

At a data transmitting side, as shown in FIG. 1, a mapping method in anOTN according to an embodiment of the present invention includes:

S1: Constructing an ODTU according to an amount M of tributary slots ofan HO OPU to be occupied by an LO ODU.

S2: Mapping the LO ODU to a payload area of the ODTU in an M-bytegranularity.

S3: Encapsulating overhead information to the payload area of the ODTU.

S4: Multiplexing the ODTU, which has been mapped the LO ODU andencapsulated with the overhead information, to the HO OPU.

The above method provides an efficient and universal mode for mappingthe LO ODU to the HO OPU.

The implementation processes of these steps in some specificapplications are described in detail as follows.

The step S1, constructing an ODTU according to an amount M of tributaryslots of an HO OPU to be occupied by an LO ODU, may include:

S11: Determining the amount M of the tributary slots of the HO OPU to beoccupied by the LO ODU.

Specifically, the amount M of the tributary slots of the HO OPU to beoccupied by the LO ODU may be determined according to the rate of the LOODU and the rate of a single tributary slot of the HO OPU, i.e. M=upperrounding of (the rate of the LO ODU/the rate of a single tributary slotof the HO OPU).

For example, as shown in FIG. 2, a HO OPU2 is divided into eight 1.25 Gtributary slots, and eight frames of HO OPU2 forms a large multi-frame.If the rate of a certain LO ODU is 6 G, then it needs to occupy fivetributary slots of the HO OPU2, and thus M equals 5 (i.e. M=upperrounding of 6/1.25). Five tributary slots of the HO OPU2 may beallocated to the current LO ODU according to the usage conditions of thetributary slots in the HO OPU. Herein the five tributary slots allocatedto the current LO ODU are assumed to be tributary slots 2, 3, 5, 7 and8.

Of course, other methods may also be used to determine M and allocatethe tributary slots to be occupied. The manner for determining M is notlimited by the embodiments of the present invention, and shall fallwithin the protection scope of the embodiments of the present invention.

S12: Constructing the ODTU.

The ODTU includes M tributary slots, and further includes JustificationControl Overhead (JC OH) corresponding to JC OH position of the HO OPU.As shown in FIG. 2, the ODTU includes the tributary slots 2, 3, 5, 7 and8 in the multi-frame formed of eight HO OPUs, and further includes JC OHposition of HO OPU frames to which the respective tributary slotscorrespond. The shaded portions in FIG. 2 correspond to the ODTU.

The step S2, mapping the LO ODU to a payload area of the ODTU in anM-byte granularity, may include:

S21: determining an amount of LO ODU(s) of M-bytes to be mapped whenmapping in the M-byte granularity, according to an amount X of the LOODU(s) to be transmitted during each multi-frame period, and herein isrepresented as C8M; in another embodiment of the present invention,determining clock information according to the amount X of the LO ODU(s)to be transmitted during each multi-frame period, clock information isdetermined and herein is represented as C8-delta. The above twoinformation items are jointly represented as “C8M+C8-delta” information.

The manner for acquiring the amount X is known, and hence is notdescribed in the embodiments of the present invention.

Specifically, the embodiment of the present invention may use thefollowing method to determine “C8M+C8-delta”:

1. Calculating C8M, MAX according to:

-   -   C8M, MAX=(LO ODU rate * LO ODU maximum frequency deviation)/(M *        TS rate * TS minimum frequency deviation) * 15232

2. Calculating C8M, MIN according to:

-   -   C8M, MIN=(LO ODU rate * LO ODU minimum frequency deviation)/(M *        TS rate * TS maximum frequency deviation) * 15232

3. Calculating C8, MAX according to:

-   -   C8, MAX=(LO ODU rate * LO ODU maximum frequency deviation)/(TS        rate * TS minimum frequency deviation) * 15232

4. Calculating C8, MIN according to:

-   -   C8, MIN=(LO ODU rate * LO ODU minimum frequency deviation)/(TS        rate *TS maximum frequency deviation) * 15232

Then C8M is an integer value within the range of [lower rounding of C8M,MIN, upper rounding of C8M, MAX], C8-delta is X−M*C8M, indicating theclock information, where X is C8, and C8 is an integer value with therange of [lower rounding of C8, MIN, upper rounding of C8, MAX].

Assuming a certain LO ODU has an amount X=76111 bytes of client data andoccupies M=5 tributary slots, then C8M=lower rounding of (X/M)=15222,and C8-delta=X−M*C8M=1. Or, C8M=lower rounding of (X/M)+1=15223, andC8-delta=X−M*C8M=−4. The mapped data information and clock informationcan be completely reflected by transmitting the “C8M+C8-delta”information, i.e. (15222, 1) or (15223, −4). The receiving side mayperceive, according to (15222, 1) or (15223, −4), that the transmittingside needs to transmit client data of 76111 bytes during one multi-frameperiod, so as to accurately recover the client clock at the receivingside.

The present invention may also use other methods to determine“C8M+C8-delta”. Meanwhile, they are not limited by the embodiments ofthe present invention, and all fall within the protection scope of thoseembodiments.

S22: Mapping the amount of the LO ODU(s) of M-byte to the payload areaof the ODTU in a M-byte granularity.

After the number of tributary slots M to be occupied by the ODTU isdetermined, the amount of the LO ODU(s) is mapped to the payload area ofthe ODTU in a M-byte granularity. This means mapping M bytes of clientdata as a unit. In the above example, M=5, mapping the amount of the LOODU(s) of M-byte to the payload area of the ODTU in the M-bytegranularity means mapping the 76111 bytes of LO ODU data in 15222 or15223 5-byte units to the payload area of the ODTU, i.e. performing themapping operation every 5 bytes of LO ODU, and totally mapping for15,222 or 15,223 times.

Specifically, the sigma-delta algorithm or other Generic MappingProcedure (GMP) mapping methods may be used to map the LO ODU(s) to thepayload area of the ODTU, as long as the other GMP mapping methods meetthe following characteristics:

1. being capable of automatically determining a filling amount accordingto the mapped signals and the rate of a target container;

2. being capable of automatically determining distribution positions ofthe filling and mapping signals in the target container according to themapped signals and the rate of the target container; and

3. transporting position information carrying the filling and mappingsignals in the overhead of the target container.

The characteristic information of the GMP mapping method in theembodiments of the present invention is further described with thefollowing two mapping modes, but is not limited by the two mappingmodes.

Mapping mode 1: evenly distributing filling data and mapping signal datato the payload area through the sigma-delta algorithm. Information suchas positions of the filling and mapping signals is carried andtransported by the overhead of the target container. The effect afterthe mapping is shown in FIG. 3, where S is filling data and D is mappingsignal data, and the filling data and the mapping signal data are evenlydistributed to the payload area.

Mapping mode 2: concentratedly placing the filling data in a fixedposition of the payload area, and determining which portions in thepayload area are for the filling data and which portions in the payloadarea are for the mapping signal data according to the filling amount.Information such as positions of the filling and mapping signals iscarried and transported by the overhead of the target container. Theeffect after the mapping is shown in FIG. 4, where S is the filling dataand D is the mapping signal data.

The step S3, encapsulating overhead information to the payload area ofthe ODTU, may include the following:

In an embodiment of the present invention, the overhead informationincludes the amount information of the LO ODU(s) of M-byte, andencapsulating the overhead information to the overhead area of the ODTUincludes encapsulating the amount information of the LO ODU(s) of M-byteunits to the overhead area of the ODTU.

Specifically, various ways may be used in encapsulating the amountinformation of the LO ODU(s) to the overhead area of the ODTU, and someexamples include:

1) directly encapsulating the amount information of the LO ODU(s) ofM-byte to the overhead area of the ODTU, and a form of “C8M” may beused;

2) dividing the amount information of the LO ODU(s) of M-byte into afixed portion of the amount information of the LO ODU(s) of M-byte and avariable portion of the amount information of the LO ODU(s) of M-byte,and encapsulating the fixed portion of the amount information of the LOODU(s) of M-byte and the variable portion of the amount information ofthe LO ODU(s) of M-byte to the overhead area of the ODTU; transportingin a form of this overhead information may also achieve the same effect.Specifically, a form of “C8M-base+C8M-delta” may be adopted, whereC8M-base+C8M-delta equivalent to C8M, indicating an amount of M-bytes inthe LO ODU(s) mapped to the payload area of the ODTU; C8M-base is anamount of M-bytes in the fixed portion, and C8M-delta is an amount ofM-bytes in the variable portion;

3) determining amount information of the LO ODU(s) of M-byte units to befilled according to the amount information of the LO ODU(s) of M-byte,and encapsulating the amount information of the LO ODU(s) of M-byte tobe filled to the overhead area of the ODTU. Transmitting in a form ofthis overhead information may also achieve the same effect.Specifically, a form of “S8M” may be adopted, where S represents thefilling data, S8M indicates an amount of filled bytes in the ODTU afterthe LO ODU(s) are mapped to the ODTU, and S8M=15232−C8M.

In another embodiment of the invention, the overhead information mayinclude the amount information of the LO ODU(s) of M-byte units and theclock information, and the step S3,encapsulating the overheadinformation to the payload area of the ODTU may include encapsulatingthe amount information of the LO ODU(s) of M-byte and the clockinformation to the overhead area of the ODTU.

Specifically, various ways may be used in encapsulating the amountinformation of the LO ODU(s) of M-byte and the clock information to theoverhead area of the ODTU, and some examples include:

1) directly encapsulating the amount information of the LO ODU(s) ofM-byte and the clock information to the overhead area of the ODTU, and aform of “C8M+C8-delta” may be used;

2) dividing the amount information of the LO ODU(s) of M-byte units intoa fixed portion and a variable portion, and encapsulating the fixedportion of the amount information of the LO ODU(s) of M-byte and thevariable portion to the overhead area of the ODTU. Transporting in aform of this overhead information may also achieve the same effect.Specifically, a form of “C8M-base+C8M-delta+C8-delta” may be used, whereC8M-base+C8M-delta equivalents to C8M, indicating the quantity of M-byteunits in the LO ODU(s) mapped to the payload area of the ODTU; C8M-baseis the quantity of M-byte units in the fixed portion, and C8M-delta isthe quantity of M-byte units in the variable portion;

3) determining amount information of the LO ODU(s) of M-byte to befilled, and encapsulating the amount information of the LO ODU(s) ofM-byte to be filled to the overhead area of the ODTU. Transporting in aform of this overhead information may also achieve the same effect.Specifically, a form of “S8M+S8-delta” may be adopted, where Srepresents the filling data, S8M indicates an amount of filled bytes inthe ODTU after the LO ODU(s) are mapped to the ODTU, S8M=15232−C8M, andS8-delta indicates the clock information.

Encapsulating the overhead information to the overhead area of the ODTUmay include encapsulating the overhead information to an overheadcorresponding to a first tributary slot or a last tributary slot in theODTU.

The overhead information indicates clock information and an amount ofthe LO ODU(s) of M-byte mapped to the ODTU in next n multi-frames, orindicates clock information and an amount of the LO ODU(s) of M-bytemapped to the ODTU in next n frames, where n is a natural number.

In an embodiment of the present invention, the “C8M+C8-delta”information indicates conditions of the clock information and an amountof M-byte units in the LO ODU(s) mapped to the ODTU in the nextmulti-frame.

If the “C8M+C8-delta” information is encapsulated to the JC OHcorresponding to the first tributary slot in the ODTU, i.e. the JC OHposition of the 2 ^(nd) frame of HO OPU corresponding to the tributaryslot 2 in the current multi-frame, then the mapping process is shown inFIG. 5. If the “C8M+C8-delta” information is encapsulated to the JC OHcorresponding to the last tributary slot in the ODTU, i.e. the JC OHposition of the 8 ^(th) frame of HO OPU corresponding to the tributaryslot 8 in the current multi-frame, then the mapping process is shown inFIG. 6.

In another one embodiment of the invention, the“C8M-base+C8M-delta+C8-delta” information indicates conditions of theclock information and an amount of M-byte units in the LO ODU(s) mappedto the ODTU in the next frame of HO OPU.

Also taking HO OPU2 as an example, in the embodiment, as shown in FIG.7, encapsulating “C8M-base+C8M-delta+C8-delta” to the JC OH positions ofthe 2 ^(nd), 3 ^(rd), 5 ^(th), 7 ^(th) and 8 ^(th) frames of HO OPU2corresponding to tributary slots 2, 3, 5, 7 and 8 in the currentmulti-frame, respectively. The information “C8M-base+C8M-delta+C8-delta”at the 2 ^(nd), 3 ^(rd), 5 ^(th), 7 ^(th) and 8 ^(th) frames of HO OPU2indicate clock information and amounts of M-byte units in the LO ODU(s)mapped to the payload area of the ODTU in the next frame of HO OPU2,respectively. The amount of M-byte units in the LO ODU(s) mapped to thepayload area of the ODTU in other frames of HO OPU2 is C8M-base; i.e.indicating mapping C8M-base+C8M-delta M-byte data of the LO ODU(s) in anM-byte granularity to the ODTU payload areas in the 3 ^(rd), 4 ^(th), 6^(th) and 8 ^(th) frames of HO OPUs in the current multi-frame and theODTU payload area in the 1 ^(st) frame of HO OPU in the nextmulti-frame. Mapping C8M-base M-byte data of the LO ODU(s) in an M-bytegranularity to the ODTU payload areas in the 2 ^(nd), 5 ^(th) and 7^(th) frames of HO OPUs.

In the embodiment of the present invention, the information“C8M-base+C8M-delta+C8-delta” may be encapsulated in the following mode,but not limited thereby, as shown in FIG. 8.

In which, C8M-base occupies 13 bits, C8M-delta occupies 3 bits, C8-deltaoccupies 8 bits, and FEC occupies 8 bits; herein the FEC errorcorrecting function is added, and an encoding mode of BCH (16, 12) maybe used to achieve an effect of correcting an error of 1 bit, andimprove the reliability of the information “C8M-base+C8M-delta+C8-delta”during transportation. In addition, the FEC may also be replaced by CRC,and the information “C8M-base+C8M-delta+C8-delta” received at thereceiving side is ensured as correct through a CRC verification.

The step S4, multiplexing the ODTU, which has been mapped the LO ODU andencapsulated with the overhead information, to the HO OPU, follows thestep S3.

The mapping method in an OTN according to the embodiment of the presentinvention not only provides a high-efficient and universal mode formapping the LO ODU to the HO OPU, compatible with processes of mappingLO ODU to HO OPU in different granularities for the convenience ofinterconnection, but also separates the data information from the clockinformation to mapping in a large granularity, and carries the clockinformation with the byte granularity to solve the problem of poorperformance of clock recovered at the receiving side caused by mappingonly with large granularity.

Correspondingly, at the data receiving side, as shown in FIG. 9, theembodiment of the present invention further provides a de-mapping methodin an OTN, for parsing an HO OPU to determine an ODTU and an amount M oftributary slots occupied by the ODTU; and de-mapping an LO ODU from apayload area of the ODTU in an M-byte granularity.

De-mapping the LO ODU from the payload area of the ODTU in the M-bytegranularity includes:

acquiring information of an amount of the LO ODU of M-byte from theoverhead of the ODTU; and

de-mapping the amount of the LO ODU of M-byte from the payload area ofthe ODTU in the M-byte granularity.

De-mapping the LO ODU of M-byte from the payload area of the ODTU in theM-byte granularity further includes:

acquiring clock information from the overhead of the ODTU, andrecovering the clock of client service according to the clockinformation.

As shown in FIG. 10, the embodiment of the present invention furtherprovides a mapping apparatus in an OTN, including:

a constructing unit, configured to construct an ODTU according to anamount M of tributary slots of an HO OPU to be occupied by an LO ODU;

a mapping unit, configured to for map the LO ODU to a payload area ofthe ODTU in an M-byte granularity;

an encapsulating unit, configured to encapsulate overhead information tothe payload area of the ODTU; and

a multiplexing unit, configured to multiplex the ODTU, which has beenmapped the LO ODU and encapsulated with the overhead information, to theHO OPU.

As shown in FIG. 11, another embodiment of the present inventionprovides a mapping apparatus in an OTN, including the constructing unit,the mapping unit, the encapsulating unit and the multiplexing unit asshown in FIG. 10, where the mapping unit includes:

a determining module, configured to determine an amount of the LO ODU ofM-byte to be mapped when mapping in an M-byte granularity, according toan amount X of the LO ODU to be transmitted in each multi-frame period;

a mapping module, configured to map the amount of the LO ODU of M-byteto the payload area of the ODTU in the M-byte granularity; and

the encapsulating unit is configured to encapsulate the amountinformation of the LO ODU of M-byte to the overhead area of the ODTU.

In another embodiment of the present invention, the determining moduleis further adopted for determining clock information according to theamount X of the LO ODU to be transmitted during each multi-frame period;and

the encapsulating unit is further configured to encapsulate the clockinformation to the overhead area of the ODTU.

As shown in FIG. 12, the embodiment of the present invention furtherprovides a de-mapping apparatus in an OTN, including:

a parsing unit, configured to parse an HO OPU to determine an ODTU andan amount M of tributary slots occupied by the ODTU; and

a de-mapping unit, configured to de-map an LO ODU from a payload area ofthe ODTU in an M-byte granularity.

The detailed contents about signal processing and executions among thecomponents of the above apparatuses are based on the same concept of themethod embodiments of the present invention, please refer to thedescriptions of the method embodiments of the present invention, andherein are not described.

The above descriptions are just some exemplary embodiments of thepresent invention, and the protection scope of the present invention isnot limited thereby. Any modification or substitution that can be easilyconceived by a person skilled in the art within the technical scopedisclosed by the present invention shall be covered by the protectionscope of the present invention. Therefore, the protection scope of thepresent invention shall be subject to that of the claims.

What is claimed is:
 1. A method for processing data in an OpticalTransport Network (OTN), comprising: mapping a Lower Order OpticalChannel Data Unit (LO ODU) signal into a payload area of an OpticalChannel Data Tributary Unit (ODTU) signal in units of M bytes, wherein Mis equal to the number of time slots of a Higher Order Optical ChannelPayload Unit (HO OPU) that are to be occupied by the ODTU signal, and Mis an integer larger than 1; encapsulating overhead information to anoverhead area of the ODTU signal; and multiplexing the ODTU signal intothe HO OPU.
 2. The method according to claim 1, wherein the overheadinformation comprises information indicating the number of M-byte dataunits of the LO ODU signal that are mapped during a multi-frame period.3. The method according to claim 2, wherein the overhead informationfurther comprises clock information that is determined according to thenumber of M-byte data units.
 4. The method according to claim 1, whereinthe overhead information is presented in an overhead area correspondingto the first tributary slot or the last tributary slot among tributaryslots that are occupied by the ODTU signal.
 5. An apparatus forprocessing data in an Optical Transport Network (OTN), comprising: aprocessor and a computer readable medium having a plurality of computerexecutable instructions stored thereon which, when executed by theprocessor, cause the processor to: mapping a Lower Order Optical ChannelData Unit (LO ODU) signal into a payload area of an Optical Channel DataTributary Unit (ODTU) signal in units of M bytes, wherein M is equal tothe number of tributary slots of a Higher Order Optical Channel PayloadUnit (HO OPU) that are to be occupied by the ODTU signal, and M is aninteger larger than 1; encapsulating overhead information to an overheadarea of the ODTU signal; and multiplexing the ODTU signal into the HOOPU.
 6. The apparatus according to claim 5, wherein the overheadinformation comprises information indicating the number of M-byte dataunits of the LO ODU signal that are mapped during a multi-frame period.7. The apparatus according to claim 6, wherein the overhead informationfurther comprises clock information that is determined according to thenumber of M-byte data units.
 8. The apparatus according to claim 5,wherein the overhead information is presented in an overhead areacorresponding to the first tributary slot or the last tributary slotamong tributary slots that are occupied by the ODTU signal.
 9. A methodfor processing data in an Optical Transport Network (OTN), comprising:parsing a Higher Order Optical Channel Payload Unit (HO OPU) to obtainan Optical Channel Data Tributary Unit (ODTU) signal; and de-mapping aLower Order Optical Channel Data Unit (LO ODU) signal from a payloadarea of the ODTU signal in units of M bytes, wherein M is equal to thenumber of tributary slots of the HO OPU that are occupied by the ODTU,and M is an integer larger than
 1. 10. The method according to claim 9,wherein the de-mapping comprises: acquiring, from an overhead of theODTU, the number of M-byte data units of the LO ODU signal that havebeen mapped into the payload area of the ODTU; and de-mapping the LO ODUsignal from the payload area of the ODTU signal in units of M bytesaccording to the number of M-byte data units.
 11. The method accordingto claim 10, wherein the overhead information is presented in anoverhead area corresponding to the first tributary slot or the lasttributary slot among tributary slots that are occupied by the ODTUsignal.
 12. An apparatus for processing data in an Optical TransportNetwork (OTN), comprising: a processor and a computer readable mediumhaving a plurality of computer executable instructions stored thereonwhich, when executed by the processor, cause the processor to: parsing aHigher Order Optical Channel Payload Unit (HO OPU) to obtain an OpticalChannel Data Tributary Unit (ODTU) signal; and de-mapping a Lower OrderOptical Channel Data Unit (LO ODU) signal from a payload area of theODTU signal in units of M bytes, wherein M is equal to the number oftributary slots of the HO OPU that are occupied by the ODTU, and M is aninteger larger than
 1. 13. The apparatus according to claim 12, whereinde-mapping in units of M bytes to obtain a Lower Order Optical ChannelData Unit (LO ODU) signal from a payload area of the ODTU signalcomprises: acquiring, from an overhead of the ODTU, the number of M-bytedata units of the LO ODU signal that have been mapped into the payloadarea of the ODTU; and de-mapping the LO ODU signal from the payload areaof the ODTU signal in units of M bytes according to the number of M-bytedata units.
 14. The apparatus according to claim 13, wherein theoverhead information is presented in an overhead area corresponding tothe first tributary slot or the last tributary slot among tributaryslots that are occupied by the ODTU signal.